Spectrometry has hitherto been used to measure characteristics of a measured object by placing the measured object on an aperture array, applying an electromagnetic wave to the aperture array and analyzing a transmittance spectrum thereof or the like. A specific example of the method is a method for measuring the characteristics of a protein (measuring object) by applying a terahertz wave to a metal mesh (one type of aperture array) to which the protein is attached and analyzing a transmittance spectrum thereof.
In such spectrometry, it is common to increase the frequency of the electromagnetic wave and correspondingly decrease the aperture area of apertures in order to increase measurement sensitivity. This is necessary because of limitations on the use of the aperture array which require that the thickness of the aperture array be substantially equal to or more than the wavelength of the applied electromagnetic wave. In particular, the thickness of an aperture array used when a high-frequency (short-wavelength) electromagnetic wave, such as a terahertz wave, is applied is considerably small. For this reason, when the aperture array is held on a stage of a spectroscope, it is sometimes bent (deflected) or creased which may cause measurement errors.
Regarding this point, International Publication No. 2011/070817 proposes a metal mesh device in which an aperture array is clamped by frame members. Since the aperture array can be held and kept in a tensioned manner in this metal mesh device, the above-described deflection and creasing can be suppressed.